This invention relates to the field of depositing films or coatings on a substrate.
Thermal barrier coatings (TBCs) are a type of film that is deposited on a substrate. A variety of techniques have been examined to fabricate TBCs, but to date only two processing routes have been successfully scaled up to produce thick TBCs, typically about 250 .mu.m. These are the electron beam assisted physical vapour deposition (EB-PVD) and plasma spraying techniques which make extensive use of vacuum and sophisticated deposition equipment.
However, the above fabrication routes are expensive for large area units and mass production. Moreover, EB-PVD is a line-of-sight process which limits the capability of the method to coat three-dimensional components uniformly.
A new technique termed electrostatic spray assisted vapour deposition (ESAVD) is described in PCT/GB96/03 105 and U.S. application Ser. No. 09/091,456, filed Jun. 15, 1998. ESAVD is a novel processing technique which offers a simple and cost effective method to manufacture ceramic films.
However, depositing the thick films that are generally required for TBCs has remained a problem.